In a known manner, a contactor has two roles, firstly to displace the launcher which supports the pinion of the starter by means of a pivoting lever, such as to allow the pinion to engage on the ring of the thermal engine to be started, and secondly to supply the electric motor of the starter, making it possible to rotate the pinion.
For this purpose, as shown in FIG. 1, the contactor 1 is provided with a fixed core 2, a mobile core 3, and a metal housing 5 in which there is provided a set of coils 6a, 6b fitted on an insulating annular support 9.
An end of the mobile core 3 is connected to the pivoting lever 10. The other end of the mobile core 3 is designed to act on the rear end of a control rod 13 by thrusting through a central bore 16 in the fixed core 2, in which the rear part of the rod 13 is fitted such as to slide.
The control rod 13 supports a contact plate 17, which is fitted such as to slide on the control rod 13. The contact plate 17 extends transversely, in order to be able to cooperate with two electrical terminals 18, 19 of an electric power circuit and establish electrical contact between them.
The control rod 13 supports a compression spring 21 which is provided between a shoulder 131 and the contact plate 17. The contactor 1 also comprises a return spring 22, provided between the cover 25 and a stop 132 of the control rod 13.
The mobile core 3 is mobile between a position, known as the position of rest, in which the mobile core 3 is in a position spaced from the fixed core 2, and a position, known as the magnetised position, in which the mobile core 3 is in contact with the fixed core 2 further to the activation of the set of coils 6a, 6b, thus generating a magnetic field for attraction of the mobile core 3 towards the fixed core 2.
In addition, the control rod 13, displaced by the mobile core 3, is mobile between a position of rest and a supply position, in which the contact plate 17 establishes contact with the electrical terminals 18, 19 when the mobile core 3 is in the magnetised position.
In order to increase the service life of the contactor 1 for applications of the stop and start type in which the starter is in heavy use, document FR2994504 teaches the use of a contactor 1 provided with a control rod 13 comprising a shoulder 131 which abuts the fixed core 2 when the rod 13 is in the position of rest. The stresses are thus distributed on the rod 13, and not on the contact plate 17, as is the case with other types of devices.
The problem of a configuration of this type is that the shoulder 131 shuts off the flow of air generated by the displacement of the mobile core 3, which leads to slowing down of the speed of displacement of the core 3, from the position of rest to the magnetised position. FIG. 2 thus shows that at the moment of establishment of the contact of the contact plate 17 with the terminals 18, 19, the speed of the mobile core 3 at the end of the course is approximately 0.8 m/s (cf. point O1). However a speed of this type is not sufficient to break the ice which may have formed on the electrical terminals 18, 19 in the case of low temperature.